1. Field of the Invention
The present invention relates to apparatus and processes for packaging microelectronic dice. In particular, the present invention relates to a packaging technology that encapsulates a microelectronic die with an encapsulation material and utilizes a metallization layer to attach a heat spreader to the microelectronic die.
2. State of the Art
Higher performance, lower cost, increased miniaturization of integrated circuit components, and greater packaging density of integrated circuits are ongoing goals of the computer industry. As these goals are achieved, microelectronic dice become smaller. Of course, the goal of greater packaging density requires that the entire microelectronic die package be equal to or only slightly larger (about 10% to 30%) than the size of the microelectronic die itself. Such microelectronic die packaging is called a “chip scale packaging” or “CSP”. However in such true CSP, the surface area provided by the microelectronic die active surface generally does not provide enough surface for all of the external contacts needed to contact the external component (not shown) for certain types of microelectronic dice (i.e., logic).
Additional surface area can be provided through the use of an interposer, such as a substrate (substantially rigid material) or a flex component (substantially flexible material) FIG. 18 illustrates a substrate interposer 222 having a microelectronic die 224 attached to and in electrical contact with a first surface 226 of the substrate interposer 222 through small solder balls 228. The small solder balls 228 extend between contacts 232 on the microelectronic die 224 and conductive traces 234 on the substrate interposer first surface 226. The conductive traces 234 are in discrete electrical contact with bond pads 236 on a second surface 238 of the substrate interposer 222 through vias 242 that extend through the substrate interposer 222. External contacts 244 (shown as solder balls) are formed on the bond pads 236. The external contacts 244 are utilized to achieve electrical communication between the microelectronic die 224 and an external electrical system (not shown).
The use of the substrate interposer 222 requires number of processing steps. These processing steps increase the cost of the package. Additionally, even the use of the small solder balls 228 presents crowding problems which can result in shorting between the small solder balls 228 and can present difficulties in inserting underfilling between the microelectronic die 224 and the substrate interposer 222 to prevent contamination and provide mechanical stability.
FIG. 19 illustrates a flex component interposer 252 wherein an active surface 254 of a microelectronic die 256 is attached to a first surface 258 of the flex component interposer 252 with a layer of adhesive 262. The microelectronic die 256 is encapsulated in an encapsulation material 264. Openings are formed in the flex component interposer 252 by laser abalation through the flex component interposer 252 to contacts 266 on the microelectronic die active surface 254 and to selected metal pads 268 residing within the flex component interposer 252. A conductive material layer is formed over a second surface 272 of the flex component interposer 252 and in the openings. The conductive material layer is patterned with standard photomask/etch processes to form conductive vias 274 and conductive traces 276. External contacts are formed on the conductive traces 276 (shown as solder balls 278 surrounded by a solder mask material 282 proximate the conductive traces 276).
Another problem arising from the fabrication of a smaller microelectronic dice is that the density of power consumption of the integrated circuit components in the microelectronic dice has increased, which, in turn, increases the average junction temperature of the dice. If the temperature of the microelectronic die becomes too high, the integrated circuits of the semiconductor die may be damaged or destroyed. Furthermore, for microelectronic dice of equivalent size, the overall power increases which presents the same problem of increased power density.
Thus, it may be necessary to attach a heat spreader to the microelectronic die. FIG. 20 illustrates a heat spreader 288 attached to the microelectronic die 256 as shown in FIG. 19. However, prior to attaching the heat spreader 288 to the microelectronic 256, a back surface 286 of the microelectronic die 256 must be exposed. This is generally achieved by grinding away the back surface 284 (see FIG. 19) of the encapsulation material 264 which can damage the microelectronic die 256.
Therefore, it would be advantageous to develop new apparatus and techniques to expose the back surface of a microelectronic die for attachment of a heat spreader with potentially damaging the microelectronic die.